Low cycle fatigue data evaluation for a high-strength spring steel

In the present investigation, low cycle fatigue (LCF) behavior is studied using the cylindrical smooth specimens under strain-controlled fully-reversed pull-push conditions for a high-strength spring steel heat-treated to different strength levels. During strain cycling the steel exhibits continuous softening independent of the applied strain levels and heat-treatments. Under the circumstances the saturation of the plastic strain energy density per cycle proves to be a valid criterion to determine the stable hysteresis loops for the cyclic stress-strain (CSS) curve formation. The strain-life curve calculated on the basis of the CSS relationship is in good agreement with the experimental counterpart, indicating a fine consistency between data from the CSS approach and from the strain-life approach. Then the LCF properties are discussed with regard to their dependence on the heat-treatments or strength levels of the steel. (C) 1997 Elsevier Science Ltd.